This is a revised application for a K23 award for Dr. Henry Chong Lee, a neonatologist at the University of California, San Francisco. Dr. Lee is establishing himself as a young investigator in clinical research of quality improvement in neonatology. This K23 award will provide Dr. Lee with the support necessary to accomplish the following goals: (1) to become expert at survey and qualitative research methods; (2) to conduct clinical investigations of the factors influencing breast milk feeding in premature infants; (3) to gather data for the purpose of designing an intervention to promote breast milk feeding in premature infants; (4) to progress in leadership in quality improvement research in neonatology; and (5) to develop an independent clinical research career. To achieve these goals, Dr. Lee has assembled a mentoring team comprised of primary mentor Dr. R. Adams Dudley, Professor of Medicine and Health Policy at UCSF, a leader in largescale health services research; two co-mentors: Dr. Jeffrey Gould, a neonatologist and Professor at Stanford, a distinguished leader and researcher in quality improvement and Director of the California Perinatal Quality Care Collaborative, and Dr. Daniel Dohan, an expert in qualitative research methods in the Institute of Health Policy Studies at UCSF; and four scientific advisors: Dr. Jane Morton, an expert in breastfeeding and breast milk provision for premature infants, Dr. Yao Sun, Medical Director of the Division of Neonatology at UCSF and expert in information technology, who is concerned with patient safety and quality of care, Ralph Gonzales, Professor of Medicine and Epidemiology & Biostatics at UCSF, an expert in Implementation Sciences, and Dr. Anna Npoles, an expert in ethnic and racial disparities in medical care. Breast milk is established as the optimal feeding choice for premature infants as it prevents serious morbidities such as necrotizing enterocolitis. Nevertheless, many premature infants are not being fed breast milk by the time they are discharged home from the hospital. Breast milk provision for premature infants varies by socio-demographic and medical factors and varies widely by hospital. Dr. Lee's research will focus on the maternal, clinician, and hospital factors that impact breast milk feeding of premature infants. The results of his study will inform the design of an intervention to promote breast milk feeding in premature infants. In Aim 1, Dr. Lee will perform a qualitative study using semi-structured interviews and a survey study of mothers to probe maternal factors related to pumping/feeding practices, focusing on the impact of early counseling and environmental factors. In Aim 2, Dr. Lee will use a case study approach of high-performing and low-performing hospitals to determine what hospital factors impact breast milk feeding of premature infants. In Aim 3, Dr. Lee will perform a statewide survey of more than 100 hospitals in California, in which he will study what clinical practices were associated with higher or lower rates of breast milk provision in premature infants. This research will form the basis for development of a pilot intervention to be proposed in an R03 grant application during the K award, and a subsequent multi-center intervention to promote breast milk feeding in premature infants, to be proposed in an R01 grant application at the end of the K award.